Abstract

We measured the photosynthetic capacity (RuBP carboxylation and electron transport capacity at 25°C) and the maximum photochemical efficiency (Fv/Fm) from autumn to spring in saplings of two evergreen broadleaf tree species and examined the negative effects of photoinhibition on the photosynthetic capacity. Saplings were grown in pots under three simulated natural light environments typical of temperate forests: an open site, deciduous understorey and evergreen understorey. During winter, the photosynthetic capacity and Fv/Fm synchronously decreased in leaves in the sun, but not those in the shade. We found large differences in Fv/Fm and photosynthetic capacity, along with a positive correlation between Fv/Fm and the photosynthetic capacity among leaves in different light environments. In photoinhibited leaves that were transferred to the shade in mid-winter, photosynthetic capacity increased synchronously with the increment of Fv/Fm. The decrease in photosynthetic capacity in photoinhibited leaves and the synchronous recovery of photosynthetic capacity with photoinhibition supported the hypothesis that photoinhibition depressed the photosynthetic capacity during winter. We showed that difference in the degree of photoinhibition was responsible for the different winter photosynthetic capacity among leaves exposed to different light environments.

Acknowledgements

We thank members of the Experimental Forest of Kyushu University for discussion, comments, encouragement and assistance in the field measurements. We also thank three anonymous reviewers for comments on the earlier version of this paper. This research was supported by a Grant-in-Aid for Scientific Research (#17380096, Leader: Kyoichi Otsuki) from the Ministry of Education, Science and Culture of Japan.

Valladares F, Pearcy RW
(2002) Drought can be more critical in the shade than in the sun: a field study of carbon gain and photo-inhibition in a Californian shrub during a dry El Nino year. Plant, Cell & Environment25, 749–759.
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